Backward reconstruction of plankton sources in the Gulf of Naples

The Gulf of Naples (GoN) is a coastal area of the Southern Tyrrhenian Sea representing a very complex system, influenced by numerous interacting factors depending on the peculiar physical and biogeochemical conditions of this area. Since 2004 a system of HF coastal radars (Sea Sonde CODAR) operates in the GoN providing real time (hourly data) surface current fields with a resolution of 1.0 × 1.0 Km over almost the entire area of the GoN. Moreover plankton abundance in the GoN is monitored weekly at the Long-Term Ecological Research station MareChiara (LTER-MC) since 1984. An oscillating population dynamics, with an alternation, especially in summer, between phases reflecting the coastal and offshore influence on the biological community, has been frequently observed at LTER-MC station. Such an opportunity to integrate biological data and current measurements at high spatio - temporal resolution, makes the GoN a natural laboratory to investigate the role of surface circulation in structuring the marine plankton community. The results here presented refer to a year-long analysis carried out for 2009, which was characterized by a very accurate estimate of the surface dynamics, with a reduced number of HF radar data gaps. A Lagrangian particle transport model, forced by the HF radar current fields, has been applied to identify probable sources and transport pathways of plankton at LTER-MC station. In particular a backward-trajectory modeling approach has been used to reconstruct a probability distribution function around the LTER-MC station. The results from the backward trajectory simulations allowed to identify origin of plankton observed at LTER-MC; the surface dynamics analysis accounted for the relationship between the inter-annual alternation in the plankton community and the variability in the wind-driven circulation.